Modelling of W UMa -type Variable Stars

16
Modelling of W UMa- Modelling of W UMa- type Variable Stars type Variable Stars Patricia Skelton Patricia Skelton MSc MSc UNISA UNISA Prof. Derck Smits Prof. Derck Smits SKA Postgraduate Bursary Conference SKA Postgraduate Bursary Conference The Wallenberg Centre, sti The Wallenberg Centre, stis 1 – 5 December 2008 1 – 5 December 2008

description

Modelling of W UMa -type Variable Stars. Patricia Skelton MSc UNISA Prof. Derck Smits SKA Postgraduate Bursary Conference The Wallenberg Centre, sti s 1 – 5 December 2008. Over-Contact System. Properties of W UMa-type Stars. Overcontact binary: Common Envelope binary - PowerPoint PPT Presentation

Transcript of Modelling of W UMa -type Variable Stars

Page 1: Modelling  of W  UMa -type Variable Stars

Modelling of W UMa-type Modelling of W UMa-type Variable StarsVariable Stars

Patricia SkeltonPatricia Skelton

MScMSc

UNISAUNISA

Prof. Derck SmitsProf. Derck Smits

SKA Postgraduate Bursary ConferenceSKA Postgraduate Bursary Conference

The Wallenberg Centre, stiThe Wallenberg Centre, stiss

1 – 5 December 20081 – 5 December 2008

Page 2: Modelling  of W  UMa -type Variable Stars

Over-Contact SystemOver-Contact System

Page 3: Modelling  of W  UMa -type Variable Stars

Properties of W UMa-type StarsProperties of W UMa-type Stars

Overcontact binary:Overcontact binary: Common Common Envelope binaryEnvelope binary Period < 1 dayPeriod < 1 day Spectral Range: A - K Spectral Range: A - K ΔΔT approximately a few hundred T approximately a few hundred degreesdegrees Subclasses : A-Type and W-TypeSubclasses : A-Type and W-Type

Page 4: Modelling  of W  UMa -type Variable Stars

ASASASAS Las Campanas Observatory, ChileLas Campanas Observatory, Chile 7cm aperture telescope7cm aperture telescope Observe once every 1 – 3 daysObserve once every 1 – 3 days 50,000+ variable stars discovered50,000+ variable stars discovered Over 5000 are EW starsOver 5000 are EW stars

Page 5: Modelling  of W  UMa -type Variable Stars

SuperWASPSuperWASP

Monitor sky for planetary transitsMonitor sky for planetary transits Two robotic observatories:Two robotic observatories:

North: La Palma, South: SAAONorth: La Palma, South: SAAO Eight wide angle cameras. Camera Eight wide angle cameras. Camera

aperture 11.1cmaperture 11.1cm Observe on a daily basisObserve on a daily basis

Page 6: Modelling  of W  UMa -type Variable Stars

ASAS

WASP

Page 7: Modelling  of W  UMa -type Variable Stars

PHOEBEPHOEBE

Page 8: Modelling  of W  UMa -type Variable Stars

Stars Of InterestStars Of Interest

Stars that display period changesStars that display period changes Stars that may be magnetically Stars that may be magnetically

active: Search for radio emissionactive: Search for radio emission Previous surveys for radio emission Previous surveys for radio emission

used distance as a search criterion. used distance as a search criterion. Flare detected from VW Cep.Flare detected from VW Cep.

Goal: Evidence for magnetic activity Goal: Evidence for magnetic activity in light curves.in light curves.

Page 9: Modelling  of W  UMa -type Variable Stars

The O’Connell EffectThe O’Connell Effect

Maxima Different HeightMaxima Different Height Magnetic Activity: SpotsMagnetic Activity: Spots

Page 10: Modelling  of W  UMa -type Variable Stars

Flux ChangesFlux Changes

8.3

8.35

8.4

8.45

8.5

8.55

8.6

8.65

1750 1950 2150 2350 2550 2750 2950 3150 3350 3550 3750

HJD ( + 2450000)

Mag

nit

ud

e

ASAS 133246-1745.5

10.4

10.5

10.6

10.7

10.8

10.9

11

11.1

1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800

HJD ( + 2450000)

Mag

nit

ud

e

ASAS 062426-2044.9

Decrease in flux

Increase in flux

Page 11: Modelling  of W  UMa -type Variable Stars

Flux ChangesFlux Changes

9.7

9.8

9.9

10

10.1

10.2

10.3

10.4

1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800

HJD ( + 2450000)

Mag

nit

ud

e

9.8

9.9

10

10.1

10.2

10.3

10.4

10.5

3850 3900 3950 4000 4050 4100

HJD ( + 2450000)

Mag

nit

ud

e

ASAS 002328-2041.8ASAS 002328-2041.8

ASAS dataASAS data

WASP dataWASP data

Combined increase & decrease in flux

Page 12: Modelling  of W  UMa -type Variable Stars

Interesting starInteresting star

ASAS 002328-2041.8

Page 13: Modelling  of W  UMa -type Variable Stars

Period ChangesPeriod Changes

ASAS Data

WASP Data

Page 14: Modelling  of W  UMa -type Variable Stars

Unanswered QuestionsUnanswered Questions

EW stars: How do they form and EW stars: How do they form and what do they become?what do they become?

Complex pattern of period changesComplex pattern of period changes Common Envelope: Uniform Common Envelope: Uniform

temperature. Why?temperature. Why?

Page 15: Modelling  of W  UMa -type Variable Stars

Future ResearchFuture Research

Period changes: O-C diagramPeriod changes: O-C diagram APT observationsAPT observations Radial velocity measurements: Mass Radial velocity measurements: Mass

ratiosratios Surveys for radio emission from Surveys for radio emission from

spots: VLA, SKAspots: VLA, SKA

Page 16: Modelling  of W  UMa -type Variable Stars

Image adapted from Binary Maker 3